I forgot to mention about the 271 MKII, because of their low sensitivity they will sound best with a solid state amplifier. A headphone amp like the O2 (Objective 2) below will improve the bass response and drive them cleanly to whatever volume you desire. The AD700, SR60 and MS1 on the other hand are highly efficient and with their low impedance mate well straight off a computer, MP3 player and receiver.

http://nwavguy.blogspot.ca/2011/07/o2-headphone-amp.html
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I’m armed and I’m drinking. You don’t want to listen to advice from me, amigo.

-Max Payne